On the ground of slow practical application of EUV (Extreme Ultra Violet) lithography as the next generation technology, an ArF liquid immersion exposure technique has been demanded to be the technique that leads to the next generation which is designed to expose around the resolution limit.
For this, an OPC (Optical Proximity Correction) in consideration of the proximity effect of light for the mask pattern correction has become an essential technique. In the OPC process, the actually transferred mask pattern has to be measured and corrected. Especially, it is important to measure the length of the specific point where the defect is likely to occur in the exposure pattern called hot spot. The importance of pattern dimension management using a CD-SEM (Critical Dimension-Scanning Electron Microscope) has been increasingly focused.
In measuring the ArF resist using the CD-SEM, the resist shrinks under the electron beam irradiation. Therefore, it is necessary to obtain the accurate shrink quantity for achievement of highly accurate length measurement.
The cross-sectional shape of the resist gives a great influence on the shape of the resist in the next process where the resist is processed into the mask. For example, trailing or constriction generated in the side wall of the resist may deteriorate accuracy of the processing dimensions. Accordingly, the need of measuring the cross-sectional shape of the resist has been increasingly demanded as well as the width dimension.
As the method for estimating the shrink quantity of the resist upon measurement using the CD-SEM, the method disclosed in Patent Literature 1 is known. The method is designed to derive the relationship (shrink curve) between the number of measurements of the resist pattern width using the CD-SEM multiple times and a change amount of the resist pattern width (shrink curve) so as to calculate the shrink quantity.
Patent Literature 2 discloses the method for obtaining information of the cross-sectional shape using an SEM image, for example. The method disclosed in Patent Literature 2 is designed to calculate image feature amount effective for estimating a cross-sectional shape of an evaluated pattern, a process condition, and a device characteristic from the SEM image of the evaluated pattern in the exposure process or the etching process. The image feature amount is subjected to a matching process with learning data for associating the cross-sectional shape of the pattern, the process condition, and the device characteristic which are preliminarily stored in the database with the image feature amount calculated from the SEM image so that the cross-sectional shape of the evaluated pattern, the process condition, and the device condition are calculated.